1. Field of the Disclosure
The present disclosure relates to electronic devices, and more particularly to electronic devices including a resistor-capacitor filter and processes of forming the same.
2. Description of the Related Art
Electronic devices can include low-pass filters that allow low-frequency signals to pass but do not allow high frequency signals to pass. The low-pass filter can be implemented as a resistor-capacitor (“RC”) circuit. When fabricating an RC low-pass filter, a capacitor structure can be formed over the substrate. For example, a lower electrode of the capacitor can be formed when forming gate electrodes, and the upper electrode of the capacitor can be formed when polysilicon resistors or other features are also being formed, for example, for load resistors within static-random-access memory (“SRAM”) cells. Thus, a double polysilicon process flow is typically used to form SRAM cells having load resistors. Alternatively, in floating gate nonvolatile memory cells, one polysilicon layer can be used to form floating gate electrodes, and another polysilicon layer can be used to form control gate electrodes. Similar to the SRAM cells, the nonvolatile memory cells can have a double polysilicon process flow and may lend itself to formation of an RC low-pass filter. However, many integrated circuits are formed with a single polysilicon process flow, and thus, a load resistor layer (after forming a gate layer) or a control gate layer (after forming a floating gate layer) is unavailable.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.